Q2 of 86 Page 153

While conducting experiments to study the effects of various stimuli on the plants, it was observed that the roots of a plant X grow and bend towards two stimuli A and B but bend away from a third stimulus C. The stem of the plant X however bends away from stimulus A and B but bends towards the stimulus C. The stimulus B is known to act on the roots due to factors related with Earth. Keeping these points in mind, answer the following questions:

a) What could be stimulus A ?


b) Name the stimulus seen in B.


c) What could be stimulus C ?

a. Stimulus A is water as roots bend towards it but shoot bends away from it. Roots are positively hydrotropic whereas shoot is negatively hydrotropic.


b. Stimulus B is gravity of earth. Roots bend towards earth gravity so it is positively geotropic whereas shoot bends away from it so it is negatively geotropic.


c. Stimulus C is light as shoot bends towards light showing positively phototropism but roots bend away from light showing negatively phototropism.


More from this chapter

All 86 →
2

Assertion (A): The loss of excess water from the aerial parts of the plant in the form of water vapour is known as transpiration.

Reason (R) : Stomata of the leaf perform transpiration.

 1

There are 3 plants A, B and C. The flowers of A open their petals in bright light during the day but close them when it gets dark at night. On the other hand, the flowers of plant B open their petals at night but close them during the day when there is bright light. The leaves of plant C fold up and droop when touched when fingers or any other solid object.

a) Name the phenomenon shown by the flowers of plant A and B.


b) Name one flower each which behaves like the flowers of plant A and B.


c) Name the phenomenon exhibited by the leaves of plant C.


d) Name a plant whose leaves behave like those of plant C.’

 3

An organism A which cannot move from one place to another makes a simple food B from the substances C and D available in the environment. The food is made in the presence of green coloured substance E present in organs F in the presence of light energy in a process called G. Some of the simple food B also gets converted into a complex food H for storage purposes. This food gives blue-black colour with iodine solution?

a) What is (i) organism A (ii) food B and food H?


b) What are C and D?


c) Name (i) green pigments E and organ F.


d) What is the process G?

 4

Imagine that student A studied the importance of certain factors in photosynthesis. He took a potted plant and kept it in dark for over 24 hours. In the early hours of the next morning, he covered one of the leaves with dark paper in the centre only. Then he placed the plant in sunlight for a few hours and tested the leaf which was covered with black paper for starch.

a) What aspect of photosynthesis was being investigated?


b) Why was the plant kept in the dark before the experiment?


c) How will you prove that starch is present in the leaves?


d) What are the other raw materials for photosynthesis?